Initial split transaction support (#1230)

* Initial split transaction support

* Add support to unsplit and edit split

* Update show.html.erb

* FIX address reviews

* Improve UX

* Update show.html.erb

* Reviews

* Update edit.html.erb

* Add parent category to dialog

* Update en.yml

* Add UI indication to totals

* FIX ui update

* Add category select like rest of app

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

test/models/entry_split_test.rb

@@ -0,0 +1,177 @@
+require "test_helper"
+
+class EntrySplitTest < ActiveSupport::TestCase
+  include EntriesTestHelper
+
+  setup do
+    @entry = create_transaction(
+      amount: 100,
+      name: "Grocery Store",
+      account: accounts(:depository),
+      category: categories(:food_and_drink)
+    )
+  end
+
+  test "split! creates child entries with correct amounts and marks parent excluded" do
+    splits = [
+      { name: "Groceries", amount: 70, category_id: categories(:food_and_drink).id },
+      { name: "Household", amount: 30, category_id: nil }
+    ]
+
+    children = @entry.split!(splits)
+
+    assert_equal 2, children.size
+    assert_equal 70, children.first.amount
+    assert_equal 30, children.last.amount
+    assert @entry.reload.excluded?
+    assert @entry.split_parent?
+  end
+
+  test "split! rejects when amounts don't sum to parent" do
+    splits = [
+      { name: "Part 1", amount: 60, category_id: nil },
+      { name: "Part 2", amount: 30, category_id: nil }
+    ]
+
+    assert_raises(ActiveRecord::RecordInvalid) do
+      @entry.split!(splits)
+    end
+  end
+
+  test "split! allows mixed positive and negative amounts that sum to parent" do
+    splits = [
+      { name: "Main expense", amount: 130, category_id: nil },
+      { name: "Refund", amount: -30, category_id: nil }
+    ]
+
+    children = @entry.split!(splits)
+
+    assert_equal 2, children.size
+    assert_equal 130, children.first.amount
+    assert_equal(-30, children.last.amount)
+  end
+
+  test "cannot split transfers" do
+    transfer = create_transfer(
+      from_account: accounts(:depository),
+      to_account: accounts(:credit_card),
+      amount: 100
+    )
+    outflow_transaction = transfer.outflow_transaction
+
+    refute outflow_transaction.splittable?
+  end
+
+  test "cannot split already-split parent" do
+    @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    refute @entry.entryable.splittable?
+  end
+
+  test "cannot split child entry" do
+    children = @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    refute children.first.entryable.splittable?
+  end
+
+  test "unsplit! removes children and restores parent" do
+    @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    assert @entry.reload.excluded?
+    assert_equal 2, @entry.child_entries.count
+
+    @entry.unsplit!
+
+    refute @entry.reload.excluded?
+    assert_equal 0, @entry.child_entries.count
+  end
+
+  test "parent deletion cascades to children" do
+    @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    child_ids = @entry.child_entries.pluck(:id)
+
+    @entry.destroy!
+
+    assert_empty Entry.where(id: child_ids)
+  end
+
+  test "individual child deletion is blocked" do
+    children = @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    refute children.first.destroy
+    assert children.first.persisted?
+  end
+
+  test "split parent cannot be un-excluded" do
+    @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    @entry.reload
+    @entry.excluded = false
+    refute @entry.valid?
+    assert_includes @entry.errors[:excluded], "cannot be toggled off for a split transaction"
+  end
+
+  test "excluding_split_parents scope excludes parents with children" do
+    @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    scope = Entry.excluding_split_parents.where(account: accounts(:depository))
+    refute_includes scope.pluck(:id), @entry.id
+    assert_includes scope.pluck(:id), @entry.child_entries.first.id
+  end
+
+  test "children inherit parent's account, date, and currency" do
+    children = @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    children.each do |child|
+      assert_equal @entry.account_id, child.account_id
+      assert_equal @entry.date, child.date
+      assert_equal @entry.currency, child.currency
+    end
+  end
+
+  test "split_parent? returns true when entry has children" do
+    refute @entry.split_parent?
+
+    @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    assert @entry.split_parent?
+  end
+
+  test "split_child? returns true for child entries" do
+    children = @entry.split!([
+      { name: "Part 1", amount: 50, category_id: nil },
+      { name: "Part 2", amount: 50, category_id: nil }
+    ])
+
+    assert children.first.split_child?
+    refute @entry.split_child?
+  end
+end